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| United States Patent |
5,055,497
|
|
Okada
, et al.
|
October 8, 1991
|
Curable resinous composition
Abstract
Curable resinous compositions which comprise (a) a metal element-containing
inorganic filler which has been treated with an oxo acid of pentavalent
phosphorus or a derivative thereof, which has the general formula:
##STR1##
wherein A.sub.1 is an organic group having at least one ethylenic double
bond capable of radical polymerization and containing 5 to 60 carbon
atoms, A.sub.2 is a hydroxyl or mercapto group, a halogen atom or an
organic group containing 1 to 60 carbon atoms, at least one of A.sub.1 and
A.sub.2 contains at least one hydrocarbyl group containing 4 to 60 carbon
atoms, X.sub.1 is an oxygen or sulfur atom and X.sub.2 is a hydroxyl or
mercapto group of a halogen atom, and (b) at least one monomer capable of
radical polymerization which is selected from the group consisting of
methacrylates and acrylates, are useful for the production of cured
articles which may be used in dentistry.
| Inventors:
|
Okada; Koichi (Kurashiki, JP);
Omura; Ikuo (Kurashiki, JP)
|
| Assignee:
|
Kuraray Company, Ltd. (Kurashiki, JP)
|
| Appl. No.:
|
324620 |
| Filed:
|
March 17, 1989 |
Foreign Application Priority Data
| Current U.S. Class: |
523/116; 523/115; 524/202; 524/710 |
| Intern'l Class: |
C08K 005/49; A61K 006/08 |
| Field of Search: |
523/115,116
524/202,710
|
References Cited
U.S. Patent Documents
| 4259117 | Mar., 1981 | Yamauchi et al. | 106/35.
|
| Foreign Patent Documents |
| 003431 | Apr., 1985 | JP.
| |
Primary Examiner: Michl; Paul R.
Assistant Examiner: Guarriello; John J.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt
Claims
What is claimed as new and desired to be secured by Letters Patent of the
United States is:
1. A curable resinous composition, which comprises:
(a) a metal element-containing inorganic filler which has been treated with
an oxo acid of pentavalent phosphorus or a derivative thereof, which has
the formula:
##STR119##
wherein A.sub.1 is an organic group having at least one ethylenic double
bond capable of radical polymerization and containing 5 to 60 carbon
atoms; A.sub.2 is a hydroxyl group, a mercapto group, a halogen atom, or
an organic group containing 1 to 60 carbon atoms; at least one of A.sub.1
and A.sub.2 contains at least one hydrocarbyl group containing 4 to 60
carbon atoms, X.sub.1 is an oxygen atom or a sulfur atom, and X.sub.2 is a
hydroxyl group, a mercapto group or a halogen atom; and
(b) at least one monomer capable of radical polymerization which is
selected from the group consisting of methacrylates and acrylates.
2. The composition of claim 1, wherein A.sub.1 is a univalent organic group
of the formula:
##STR120##
in which R.sub.1 is a hydrogen atom or a methyl group, R.sub.2 is an
organic group which contains 4 to 40 carbon atoms, contains at least one
hydrocarbyl group with 4 to 40 carbon atoms, has a valence of (m+1) and is
bound to each of the Y.sub.1 and Y.sub.2 groups with a carbon atom
contained therein, Y.sub.1 is --COO--, --COS--, or --CONR.sub.3 --, where
R.sub.3 is a hydrogen atom or a hydrocarbyl group containing 1 to 6 carbon
atoms, Y.sub.2 is an oxygen atom, a sulfur atom, or
##STR121##
m is an integer of 1 to 4, and k is an integer of 0 or 1, and wherein
A.sub.2 is a hydroxyl group, a mercapto group, or a halogen atom.
3. The composition of claim 1, wherein A.sub.1 is a univalent organic group
of the formula:
##STR122##
in which R.sub.1 is a hydrogen atom or a methyl group, R.sub.2 is an
organic group which contains 4 to 40 carbon atoms, contains at least one
hydrocarbyl group with 4 to 40 carbon atoms, has a valence of (m+1) and is
bound to each of the Y.sub.1 and Y.sub.2 groups with a carbon atom
contained therein, Y.sub.1 is --COO--, --COS--, --or CONR.sub.3 --, where
R.sub.3 is a hydrogen atom or a hydrocarbyl group containing 1 to 6 carbon
atoms, Y.sub.2 is an oxygen atom, a sulfur atom, or
##STR123##
m is an integer of 1 to 4, and k is an integer of 1 or 1; and wherein
A.sub.2 is a univalent organic group of the formula:
##STR124##
in which R.sub.1 ' is a hydrogen atom or a methyl group, R.sub.2 ' is an
organic group which contains 1 to 40 carbon atoms, has a valence of (j+1)
and is bound to each of the Y.sub.1 ' and Y.sub.2 ' groups with a carbon
atom contained therein, Y.sub.1 ' is --COO--, --COS--, or --CONR.sub.3
'--, where R.sub.3 ' is a hydrogen atom or a hydrocarbyl group containing
1 to 6 carbon atoms, Y.sub.2 ' is an oxygen atom, a sulfur atom, or
##STR125##
j is an integer of 0 to 4, and l is an integer of 0 or 1.
4. The composition of claim 1, wherein A.sub.1 is a univalent organic group
of the formula:
##STR126##
in which R.sub.1 is a hydrogen atom or a methyl group, R.sub.2 is an
organic group which contains 4 to 40 carbon atoms, contains at least one
hydrocarbyl group with 4 to 40 carbon atoms, has a valence of (m+1) and is
bound to each of the Y.sub.1 and Y.sub.2 groups with a carbon atom
contained therein, Y.sub.1 is --COO--, --COS--, or --CONR.sub.3 --, where
R.sub.3 is a hydrogen atom or a hydrocarbyl group containing 1 to 6 carbon
atoms, Y.sub.2 is an oxygen atom, a sulfur atom, or
##STR127##
m is an integer of 1 to 4, and k is an integer of 0 or 1; and wherein
A.sub.2 is a univalent organic group of the formula:
##STR128##
in which R.sub.1 ' is a hydrogen atom or a methyl group, R.sub.2 ' is an
organic group which contains 1 to 40 carbon atoms, has a valence of (j+1)
and is bound to each of the Y.sub.1 ' and Y.sub.2 ' groups with a carbon
atom contained therein, Y.sub.1 ' is --COO--, --COS--, or --CONR.sub.3
'--, where R.sub.3 ' is a hydrogen atom or a hydrocarbyl group containing
1 to 6 carbon atoms, Y.sub.2 ' is an oxygen atom, a sulfur atom, or
##STR129##
j is an integer of 0 to 4, and l is an integer of 0 or 1; X.sub.1 is an
oxygen atom or a sulfur atom; and X.sub.2 is a hydroxyl group, a mercapto
group, or a halogen atom.
5. The composition of claim 2, wherein X.sub.1 is an oxygen atom, and
X.sub.2 and A.sub.2 are each a hydroxyl group.
6. The composition of claim 2, wherein X.sub.1 is an oxygen atom, and
X.sub.2 and A.sub.2 are each a chlorine atom.
7. The composition of claim 2, wherein X.sub.1 is a sulfur atom.
8. The composition of claim 3, wherein X.sub.1 is an oxygen atom and
X.sub.2 is a hydroxyl group.
9. The composition of claim 3, wherein X.sub.1 is an oxygen atom and
X.sub.2 is a chlorine atom.
10. The composition of claim 3, wherein X.sub.1 is a sulfur atom.
11. The composition of claim 2, wherein m is 1 and R.sub.2 is a group of
the formula:
--R.sub.4 --Y.sub.3 --R.sub.5 --Y.sub.3).sub.h R.sub.4 --
in which h is an integer of 0 or 1 and, when h is 0, R.sub.4 is a
hydrocarbyl group containing 4 to 20 carbon atoms and Y.sub.3 is an oxygen
atom; and when h is 1, R.sub.4 is a hydrocarbyl group containing 2 to 9
carbon atoms, R.sub.5 is a hydrocarbon residue containing 4 to 20 carbon
atoms and Y.sub.3 is an oxygen atom, --COO-- or --OOC--.
12. The composition of claim 3, wherein m is 1 and R.sub.2 is a group of
the formula:
--R.sub.4 --Y.sub.3 --R.sub.5 --Y.sub.3).sub.h R.sub.4 --
in which h is an integer of 0 or 1 and, when h is 0, R.sub.4 is a
hydrocarbyl group containing 4 to 20 carbon atoms and Y.sub.3 is an oxygen
atom; and when h is 1, R.sub.4 is a hydrocarbyl group containing 2 to 9
carbon atoms, R.sub.5 is a hydrocarbon residue containing 4 to 20 carbon
atoms and Y.sub.3 is an oxygen atom, --COO-- or --OOC--.
13. The composition of claim 4, wherein m is 1 and R.sub.2 is a group of
the formula:
--R.sub.4 --Y.sub.3 --R.sub.5 --Y.sub.3).sub.h R.sub.4 --
in which h is an integer of 0 or 1 and, when h is 0, R.sub.4 is a
hydrocarbyl group containing 4 to 20 carbon atoms and Y.sub.3 is an oxygen
atom; and when h is 1, R.sub.4 is a hydrocarbyl group containing 2 to 9
carbon atoms, R.sub.5 is a hydrocarbon residue containing 4 to 20 carbon
atoms and Y.sub.3 is an oxygen atom, --COO-- or --OOC--.
14. The composition of claim 2, wherein m is 1 and R.sub.2 is a group of
the general formula:
--CH.sub.2 --.sub.i
in which i is an integer of 4 to 40.
15. The composition of claim 3, wherein m is 1 and R.sub.2 is a group of
the general formula:
--CH.sub.2 --.sub.i
in which i is an integer of 4 to 40.
16. The composition of claim 4, wherein m is 1 and R.sub.2 is a group of
the general formula:
--CH.sub.2 --.sub.i
in which i is an integer of 4 to 40.
17. A cured article, prepared by curing a curable resinous compositon,
which comprises:
(a) a metal element-containing inorganic filler which has been treated with
an oxo acid of pentavalent phosphorus or a derivative thereof, which has
the formula:
##STR130##
wherein A.sub.1 is an organic group having at least one ethylenic double
bond capable of radical polymerization and containing 5 to 60 carbon
atoms; A.sub.2 is a hydroxyl group, a mercapto group, a halogen atom, or
an organic group containing 1 to 60 carbon atoms; at least one of A.sub.1
and A.sub.2 contains at least one hydrocarbyl group containing 4 to 60
carbon atoms, X.sub.1 is an oxygen atom or a sulfur atom, and X.sub.2 is a
hydroxyl group, a mercapto group or a halogen atom; and
(b) at least one monomer capable of radical polymerization which is
selected from the group consisting of methacrylates and acrylates.
18. The composition of claim 1, wherein said metal element-containing
inorganic filler which has been treated with said oxo acid of pentavalent
phosphorus is prepared by a process comprising:
(i) suspending said inorganic filler and said oxo acid of pentavalent
phosphorus in a solvent selected from the group consisting of water,
alcohol, hexane, benzene, toluene, and xylene, to obtain a suspension:
(ii) stirring said suspension; and
(iii) removing said solvent from said suspension.
19. The composition of claim 1, wherein said metal element-containing
inorganic filler which has been treated with said oxo acid of pentavalent
phosphorus is prepared by a process comprising:
(i) charging said inorganic filler into a mixer; and
(ii) adding said oxo acid of pentavalent phosphorus to said mixer while
stirring.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to curable resinous compositions, which
contain an inorganic filler which has been surface-treated with an
organophosphorus compound. The present curable resinous compositions may
be used as materials for industrial use and as a biological hard tissue
materials. As examples of such materials, there may be mentioned molding
compositions, composite resins for dental use (filling and restoration
materials, materials for making inlays, artificial crowns, artificial
tooth, abutment construction materials), dental adhesives, denture base
materials, impression materials, artificial bones and bone cements.
2. Discussion of the Background
The term "curable resinous composition" as used herein means a composition
containing, as essential components, an inorganic filler and a
polymerizable monomer.
Recently, in the field of dental care, compositions containing an inorganic
filler and a polymerizable monomer, for example, composite resins for
dental use, have come into use. The inorganic fillers used in composite
resins for dental use are generally subjected to preliminary surface
treatment. The surface treatment improves the wettability at the
filler-polymerizable monomer interface, makes it possible to increase the
filler content, and improves the dispersibility of the filler in the
composition. As a result, composite resin moldings obtained by
polymerization of the monomer have improved mechanical strength owing to
good adhesion at the filler-resin interface. Known in the art as surface
treating agents for such purposes are silane coupling agents, typically
.gamma.-methacryloyloxypropyltrimethoxysilane.
More broadly, in the industrial field, there are known, as other surface
treating agents for inorganic fillers, titanate coupling agents,
zircoaluminate type coupling agents, higher alkyl alcohols, higher fatty
acids, organophosphate esters, and so forth. Among them, the
organophosphate esters are related to the present invention and therefore
are summarized below.
Japanese Patent Publication No. 60-3431 discloses inorganic fillers
surface-treated with organophosphate esters of the formula:
##STR2##
wherein R.sub.1 is a hydrogen atom or a methyl group and R.sub.2 is an
alkylene group containing 2 to 6 carbon atoms or a halogen-substituted
derivative thereof, a polyoxyethylene group of the following formula:
--CH.sub.2 --CH.sub.2 --(O--CH.sub.2 --CH.sub.2).sub.n -- (n=1 to 20)
or a polyoxypropylene group of the following formula:
##STR3##
Japanese Laid-open Patent Application Kokai No. 59-170131 discloses
inorganic powders surface-treated with one or more organophosphorus
compounds of the general formula:
##STR4##
wherein R and R' are the same or different and each is an alkyl, alkenyl,
aryl, alkoxy, alkenoxy or aryloxy group containing 1 to 30 carbon atoms or
a group derived from these organic groups by substitution.
In addition, Japanese Laid-open Patent Applications Kokai Nos. 56-54795,
57-128728, 57-168954, and 57-198735, describe similar technical ideas.
These known resinous compositions for industrial use comprise a polymer and
a surface-treated inorganic filler. Since the polymer has no or few
reactive groups, the possibility that the polymer may be bound chemically
to the surface-treating agent to a high degree is small and therefore only
limited improvements in mechanical properties are attained. Accordingly,
resinous compositions in which the resin is bound to the surface-treating
agent to a high degree and which can give good mechanical properties are
highly desirable.
Furthermore, compositions for dental use, to which an aspect of the present
invention is directed, are required to possess water resistance, which is
a very important property since the cured moldings from said compositions
may be used in the oral cavity for a prolonged period of time.
Accordingly, resinous compositions of good water resistance are also
desired.
The above-cited prior art references are not concerned with improving the
water resistance of the respective resinous compositions or of the
applicability of the compositions in dentistry. Thus, it is impossible to
anticipate from said references that the known organophosphorus compounds
might be effective in achieving the objects of the present invention.
Inorganic fillers in conventional resinous compositions, especially those
in dental use, mostly have a high silicon content (for example, silica and
silica-based glasses). Only in very rare cases, have inorganic fillers
containing a metal or a metal oxide or salt as a main constituent, been
put to practical use in resinous compositions.
As the main reason why such metal element-containing inorganic fillers have
not been used in resinous compositions, there may be mentioned the fact
that the technology of surface treatment of said fillers has not been
established. The surface treatment effect of known silane- or
titanium-containing surface-treating agents, on these inorganic fillers,
is not so remarkable as those on silica. Therefore, resinous compositions
containing large amounts of these fillers treated with known surface
treating agents suffer from disadvantages such as decreased strength (in
particular under wet conditions) or dislodgement of the filler due to
insufficient bonding at the resin-inorganic filler interface.
However, it might be expected that the use of a metal, metal oxide or metal
salt as an inorganic filler might give resinous compositions possessing
more favorable characteristics as compared with the conventional
silica-containing compositions.
For instance, replacement of silica with a metal oxide such as alumina or
zirconia might give composite resins for dental use which have an
aesthetic appearance, good mechanical strength, and good chemical
stability, and incorporation of a filler close in composition to a natural
tooth, such as hydroxyapatite, might provide dental adhesives having good
biocompatibility. The use of a metal filler could make it possible to
develop new types of composites for dental use which have ductility and
toughness.
In view of the foregoing, the possibility of a surface treatment technology
effectively applicable to the above-mentioned metal element-containing
inorganic fillers has been investigated.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide resinous
compositions which contain a surface-treated, metal element-containing
inorganic filler and a monomer capable of radical polymerization, which
yield cured articles which possess good mechanical properties.
It is another object of the present invention to provide resinous
compositions which yield cured articles which are water resistant.
It is another object of the present invention to provide resinous
compositions which exhibit good bonding at the resin-inorganic filler
interface.
It is another object of the present invention to provide resinous
compositions which contain a filler which is a metal, metal oxide, or
metal salt.
It is another object of the present invention to provide resinous
compositions which contain a filler which is a metal, metal oxide, or
metal salt and yield cured articles which possess good mechanical
strength.
It is another object of the present invention to provide resinous
compositions which contain a filler which is a metal, metal oxide, or
metal salt and yield cured articles in which the filler is not dislodged.
It is another object of the present invention to provide resinous
compositions which are biocompatible.
These and other objects which will become apparent during the course of the
following detailed description have been achieved by the present
inventors' discovery that organophosphorus compounds having a specific
molecular structure can serve as very effective surface-treating agents
for metal element-containing inorganic fillers.
Thus, the resinous composition provided by the present invention is a
curable resinous composition which comprises:
(a) a metal element-containing inorganic filler preliminarily treated with
an oxo acid of pentavalent phosphorus or a derivative thereof, which has
the general formula:
##STR5##
wherein A.sub.1 is an organic group having at least one ethylenic double
bond capable of radical polymerization and containing 5 to 60 carbon
atoms, A.sub.2 is a hydroxyl or mercapto group, a halogen atom or an
organic group containing 1 to 60 carbon atoms, at least one of A.sub.1 and
A.sub.2 contains at least one hydrocarbyl group containing 4 to 60 carbon
atoms, X.sub.1 is an oxygen or sulfur atom and X.sub.2 is a hydroxyl or
mercapto group or a halogen atom, and
(b) at least one monomer capable of radical polymerization which is
selected from the group consisting of methacrylates and acrylates.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The resinous compositions according to the present invention are preferably
used as compositions for dental use and, in the following, the invention
is described with particular reference with compositions for dental use.
It is to be noted, however, that the range of applicability of the
resinous compositions according to the invention is not limited to the
field of dentistry.
The inorganic filler to be used in the resinous composition of the present
invention is characterized in that it contains a metal element as a
component thereof. Metal elements include the elements positioned to the
left of the line connecting boron and astatine in the long form of the
periodic table, with the exclusion of hydrogen and the elements positioned
on the line, namely B, Si, As, Te, and At. Among such elements, Al, Mg,
Ca, Ti, Cr, Fe, Co, Ni, Cu, Zn, Sr, Zr, Pd, Hg, Sn, Ba, Pt, Au, and La,
for example, are particularly useful in achieving the objects of the
present invention.
The metal element can take various forms in the inorganic filler. For
example, it may be contained in the filler in the form of an oxide such as
Al.sub.2 O.sub.3, ZnO, CaO, TiO.sub.2, ZrO.sub.2, La.sub.2 O.sub.3, BaO,
Fe.sub.2 O.sub.3 or SrO.sub.2 ; a hydroxide, such as Al(OH).sub.3 ; a
halide, such as CaF.sub.2 ; a sulfate, such as BaSO.sub.4 or CaSO.sub.4 ;
a carbonate, such as CaCO.sub.3 ; a phosphate, such as CaHPO.sub.4,
Ca(H.sub.2 PO.sub.4).sub.2, Ca.sub.3 (PO.sub.4).sub.2, Ca.sub.2 P.sub.2
O.sub.7, Ca(PO.sub.3).sub.2, Ca.sub.4 P.sub.2 O.sub.9, Mg.sub.2 P.sub.4
O.sub.12, Al(PO.sub.3).sub.2 or AlPO.sub.4 ; or the like.
Such metal compounds may occur, in the inorganic filler, either as a single
component or as a constituent of a multicomponent system, such as a
ceramic or a mineral. In a multicomponent system, the system can of course
contain a plurality of metal elements and may further contain components
other than metal elements, for example SiO.sub.2, P.sub.2 O.sub.5, B.sub.2
O.sub.3, Si.sub.3 N.sub.4, SiC, B.sub.4 C and BN. As examples of such
systems, there may be mentioned K.sub.2 O.TiO.sub.2, BaO.TiO.sub.2,
CaO.Al.sub.2 O.sub.3, zircon (the SiO.sub.2 --ZrO.sub.2 system), sialon
(the SiO.sub.2 --Al.sub.2 O.sub.3 --Si.sub.3 N.sub.4 L system), La-glass
ceramics (the La.sub.2 O.sub.3 --Al.sub.2 O.sub.3 --SiO.sub.2 system; e.g
, Shott GM 31-684.RTM.), Ba-glasses (the BaO--Al.sub.2 O.sub.3 --B.sub.2
O.sub.3 --SiO.sub.2 system; e.g. Shott GM 27-884.RTM., Shott 8235.RTM.,
Ray-Sorb T-2000.RTM., Ray-Sorb T-3000.RTM.), Sr-glasses (the SrO.sub.2
--Al.sub.2 O.sub.3 --SiO.sub.2 system, e.g. Shott GM 32-087 .RTM.,
Ray-Sorb T-4000.RTM.) and, further, the so-called bioglasses, for example
various CaO--P.sub.2 O.sub.5 -containing glass ceramics and
hydroxyapatite. Furthermore, in addition to such forms as mentioned above,
metal powders as such may also be used as fillers and, in this case,
metals are used as simple substances or in the form of alloys.
In any of the fillers mentioned above, it is essential that the inorganic
filler should be substantially insoluble in water, since the resinous
composition includes dental applications in which it is used under highly
wet conditions. The term "substantially insoluble in water" as used herein
means that the inorganic filler has a saturated concentration of 0.1% by
weight or less in water at room temperature.
The inorganic filler may have any form or shape without any limitation.
Various sizes and forms, such as spherical, crushed, needle-like, whisker
and platelet forms, may be used depending on the intended use of the
composition. The particle size of the inorganic filler is not critical
but, generally, a size within the range of 5 nm to 0.5 mm is preferred.
The "particle size" as so called herein is expressed in terms of the mean
of the maximum diameter and the minimum diameter of the filler.
The most characteristic feature of the invention lies in that the above
filler is used after preliminary surface treatment with an oxo acid of
pentavalent phosphorus or a derivative thereof, which is represented by
the general formula (1) and sometimes hereinafter referred to as
"organophosphorus compound" as well. Hereinafter, the inorganic filler in
the untreated state is sometimes referred to as "inorganic filler (A)".
As particular examples of the "ethylenic double bond capable of radical
polymerization", which constitutes a structural characteristic of the
above-mentioned organophosphorus compound (1), there may be mentioned the
following:
##STR6##
Among such ethylenic double bonds, the ethylenic double bonds of acrylic
acid, methacrylic acid, or styrene are particularly preferred. When
inorganic filler (A) is treated with an organophosphorus compound which is
the same as the organophosphorus compound (1) except for the absence of
the above-mentioned double bond, the adhesion between filler and resin
matrix is very poor, and accordingly, the objects of the invention can
never be accomplished.
The term "organic group" as used herein includes:
(a) hydrocarbyl groups which may optionally have one or more substituents
selected from the group consisting of halogen, hydroxyl, carboxyl,
mercapto, cyano, phosphono, and --O--P(O)(OH).sub.2 groups,
(b) groups resulting from coupling of at least one of the above-mentioned
hydrocarbyl groups to at least one of the following linking groups:
##STR7##
and complex linking groups resulting from coupling of at least two of the
above linking groups.
The following typical examples will serve for more detailed illustration.
Examples of the hydrocarbyl groups (a) include:
##STR8##
Examples of the groups (b) derived from at least one hydrocarbyl group (a)
and at least one linking group include:
##STR9##
The hydrocarbyl groups having 4 to 60 carbon atoms, which may be contained
in at least one of the organic groups A.sub.1 and A.sub.2 of said formula
(1) are the same groups as mentioned above. Structures resulting from
substitution of the hydrocarbyl group with three or more hyrophilic
substituents, such as hydroxyl, carboxyl, phosphono, and
--O--P(O)(OH).sub.2 groups, however, are disadvantageous in achieving the
objects of the present invention since such hydrophilic substituents
decrease the hydrophobicity of the hydrocarbyl group.
When the hydrocarbyl group contains less than 4 carbon atoms, the resulting
resinous composition may often be unsatisfactory in water resistance. When
the number of carbon atoms in question is at least 4, preferably at least
5, the water resistance attained is at a level satisfactory for dental
applications. In particular, when the number of carbon atoms is at least
8, good water resistance is obtained.
The number of carbon atoms in A.sub.1 has an influence on the effects of
surface treatment. When the number of carbon atoms is within the range of
5 to 60, the effects of surface treatment are such that desirable physical
properties required for dental use can be attained. When A.sub.2 is an
organic group, the number of carbon atoms in A.sub.2 also has an influence
on the effects of surface treatment and should preferably be not more than
60.
Among the organophosphorus compounds of general formula (1), those
compounds mentioned below are particularly preferred in view of reactivity
with inorganic fillers, copolymerizability with polymerizable monomers
(b), and ease of synthesis.
(i) Compounds of general formula (1) wherein A.sub.1 is a univalent organic
group of the general formula:
##STR10##
in which R.sub.1 is a hydrogen atom or a methyl group, R.sub.2 is an
organic group which contains a total of 4 to 40 carbon atoms, contains at
least one hydrocarbyl group having 4 to 40 carbon atoms, has a valence of
(m+1) and is bound to each of the Y.sub.1 and Y.sub.2 groups with a carbon
atom contained therein, Y.sub.1 is --COO--, --COS-- or --CONR.sub.3 --
(R.sub.3 being a hydrogen atom or a hydrocarbyl group containing 1 to 6
carbon atoms), Y.sub.2 is an oxygen or sulfur atom or
##STR11##
(R.sub.3 being defined as above), m is an integer of 1 to 4 and k is an
integer of 0 or 1, and wherein A.sub.2 is a hydroxyl or mercapto group or
a halogen atom.
Preferred among the compounds (i) mentioned above compounds in which
X.sub.1 is an oxygen atom and X.sub.2 and A.sub.2 each is a hydroxyl
group. The group of these compounds is hereinafter referred to as "group
(i)-a".
##STR12##
The organophosphorus compounds (i)-a are most effective in treating base
metal element-containing inorganic fillers. As examples of the base metal
element, there may be mentioned Al, Mg, Ca, Ti, Fe, Co, Cr, Ni, Cu, Zn,
Sr, Zr, Sn, Ba, La, and Cr. The (i)-a compounds are particularly effective
in treating metal oxides such as Al.sub.2 O.sub.3, TiO.sub.2, ZrO.sub.2,
Fe.sub.2 O.sub.3, and ZnO; metal salts such as CaCO.sub.3, Ca.sub.3
(PO.sub.4).sub.2 and AlPO.sub.4 ; hydroxyapatite; and metal powders
containing Ti, Fe, Co, Cr, Ni, Cu, Zn, and Sn. Specific examples of the
group (i)-a compounds include:
##STR13##
Another preferred group of compounds, group (i)-b, includes those compounds
(i) mentioned above in which, in general formula (1), X.sub.1 is an oxygen
atom and A.sub.2 and X.sub.2 are each a halogen atom, such as chlorine,
bromine, fluorine, or iodine. When the halogen is chlorine, these
compounds may be represented by the general formula:
##STR14##
Typical examples of such compounds are as follows:
##STR15##
A third group of preferred compounds, group (i)-c, includes those compounds
(i) mentioned above in which, in general formula (1), X.sub.1 is a sulfur
atom and A.sub.2 and X.sub.2 each is a hydroxyl or mercapto group or a
halogen atom.
##STR16##
The group (i)-c organophosphorus compounds produce good effects in the
surface treatment of not only base metal element-containing inorganic
fillers but also noble metal element-containing inorganic fillers. As
examples of the noble metals, there may be mentioned Pd, Ag, Pt, and Au.
Examples of the --P(S)A.sub.2 X.sub.2 group include
##STR17##
Among the above examples,
##STR18##
has the tautomeric form
##STR19##
can occur in the tautomeric form
##STR20##
Specific examples of the (i)-c group compounds are as follows:
##STR21##
Also of value in the practice of the invention are the following compounds:
(ii) Compounds of general formula (1) wherein A.sub.1 is a univalent
organic group of the general formula:
##STR22##
in which R.sub.1, R.sub.2, Y.sub.1, Y.sub.2, m and k are as defined
hereinabove in relation to the compounds (i) and wherein A.sub.2 is a
univalent organic group of the general formula:
##STR23##
in which R.sub.1 ' is a hydrogen atom or a methyl group, R.sub.2 ' is an
organic group which contains 1 to 40 carbon atoms, has a valence of (j+1)
and is bound to each of the Y.sub.1 ' and Y.sub.2 ' groups with a carbon
atom contained therein, Y.sub.1 ' is --COO--, --COS--, or --CONR.sub.3 '--
(R.sub.3 being a hydrogen atom or a hydrocarbyl group containing 1 to 6
carbon atoms), Y.sub.2 ' is an oxygen or sulfur atom or
##STR24##
(R.sub.3 being defined as above), j is an integer of 0 to 4 and l is an
integer of 0 or 1.
Among the compounds (ii) mentioned above, those in which, in general
formula (1), X.sub.1 is an oxygen atom and X.sub.2 is a hydroxyl group
constitute a preferred group, hereinafter referred to as group (ii)-a.
##STR25##
The organophosphorus compounds of group (ii)-a are also effective in
treating base metal element-containing inorganic fillers as mentioned
above in regard to organophosphorus compounds (i)-a.
Typical examples of the compounds (ii)-a are as follows:
##STR26##
Another group (hereinafter referred to as group (ii)-b) of preferred
compounds among the compounds (ii) includes those compounds (ii) in which
X.sub.1 is an oxygen atom and X.sub.2 is a halogen atom, such as chlorine,
bromine, fluorine, or iodine.
When the halogen atom is chlorine, the (ii)-b compounds may be represented
by the structural formula:
##STR27##
The organophosphorus compounds (ii)-b, which correspond to derivatives of
the compounds (ii)-a wherein a hydroxyl group of X.sub.2 is substituted
for chlorine atom, are comparable in surface treatment effects to the
compounds (ii)-a. The same relationship exists between the groups (i)-b
and (i)-a.
Typical examples of the compounds (ii)-b are as follows:
##STR28##
Among the compounds (ii), those in which X.sub.1 is S and X.sub.2 is a
hydroxyl or mercapto group or a halogen atom are hereinafter referred to
as compounds (ii)-c, and are represented by the formula:
##STR29##
Like the organophosphorus compounds (i)-c, the compounds (ii)-c are
effective in treating base metal or noble metal-containing inorganic
fillers. The compounds (ii)-c can be synthesized more readily and have
higher stability than the compounds (i)-c and therefore can be utilized
more advantageously.
Typical examples of the
##STR30##
group in compounds (ii)-c are as follows:
##STR31##
tautomers to each other.
Typical examples of the compounds (ii)-c are as follows:
##STR32##
Furthermore, in accordance with the present invention, the following, group
(ii), organophosphorus compounds can be used as well. Group (iii)
compounds have the general formula (1), wherein A.sub.1 is a univalent
organic group of the general formula:
##STR33##
in which R.sub.1, R.sub.2, Y.sub.1, Y.sub.2, m, and k are defined as above
for the compounds (ii) and wherein A.sub.2 is a univalent organic group of
the general formula:
##STR34##
wherein R.sub.1 ', R.sub.2 ', Y.sub.1 ', Y.sub.2 ', j, and l are defined
as above for the compounds (ii) and X.sub.1 and X.sub.2 are defined as
above for the compounds (i).
Such compounds have the structural formula:
##STR35##
When neither X.sub.1 nor X.sub.2 contains a sulfur atom, the
organophosphorus compounds (iii) are as effective in treating base
element-containing fillers as the sulfur-free compounds among those
mentioned above. On the other hand, those compounds (iii) in which X.sub.1
and/or X.sub.2 contains a sulfur atom are remarkably effective also in
treating noble metal element-containing fillers, like the
sulfur-containing compounds among the compounds mentioned above. In either
case, those compounds (iii) in which R.sub.1 =R.sub.1 ', R.sub.2 =R.sub.2
', Y.sub.1 =Y.sub.1 ', Y.sub.2 =Y.sub.2 ', m=j and k=l, namely which are
symmetrical, are preferred for the reason that they can be synthesized
with ease.
Typical examples of the compounds (iii) are as follows:
##STR36##
In any of the organophosphorus compounds (i) through (iii), the group
R.sub.2 should preferably possess a long chain length but have no long,
bulky, branched side chains. The reason is presumably that when compounds
having such R.sub.2 group are used, the inorganic filler surface can be
covered to a satisfactory extent with surface treating agent molecules.
When m is equal to 1, the following is a particularly preferred structure
of R.sub.2 :
--R.sub.4 --Y.sub.3 --R.sub.5 --Y.sub.3).sub.h R.sub.4 --
wherein h is 0 or 1, and when h=0, R.sub.4 is a hydrocarbyl group
containing 4 to 20 carbon atoms and Y.sub.3 is an oxygen atom, and when
h=1, R.sub.4 is a hydrocarbyl group containing 2 to 9 carbon atoms,
R.sub.5 is a hydrocarbyl group containing 4 to 20 carbon atoms, and
Y.sub.3 is an oxygen atom, --COO-- or --OOC--.
Typical examples of R.sub.2 are as follows:
##STR37##
Another preferred structure of R.sub.2 is the following:
--(CH.sub.2).sub.i --
wherein i is an integer of 4 to 40.
In the practice of the present invention, other organophosphorus compounds,
such as shown below, may also be used suitably as surface treating agents
in addition to the above-mentioned organophosphorus compounds (i) to
(iii).
##STR38##
In synthesizing the above-described organophosphorus compounds, the
following, for instance, may serve as references: G. M. Kosolapoff,
Organophosphorus Compounds, Wiley (1950); Ye. L. L. Gefter,
Organophosphorus Monomers and Polymers, Pergamon Press (1962); The Society
of Synthetic Organic Chemistry, Japan (ed.), Modern Organic Synthesis
Series 5, Organophosphorus Compounds, Gihodo (1971); and Bielsteins
Handbuch der Organischen Chemie, Springer-Verlag.
More specifically, the methods of synthesis disclosed in Japanese Laid-open
Patent Applications Kokai Nos. 58-128393, 58-192891, 58-21687, 58-21688,
59-139392, 59-135272, 59-142268, 60-166363, 60-166364, and 57-151607 may
also be applicable.
The surface modification of inorganic fillers (A) with organophosphorus
compound (1) can be carried out by any of the methods generally known for
surface treatment of powder materials with surface treating agents and, in
brief, by the wet method or dry method.
The wet method involves suspending an inorganic filler (A) and an
organophosphorus compound (1) in an appropriate amount of a solvent such
as water, alcohol, hexane, benzene, toluene, xylene, or the like and
stirring the resulting slurry to a sufficient extent. In this case, the
optimum conditions, namely the optimum solvent, reaction temperature, and
reaction time, may vary depending on the combination of inorganic filler
(A) and organophosphorus compound (1) but can be easily determined by one
skilled in the art. After a sufficient period of stirring, the solvent is
removed by evaporation under a reduced pressure, filtration,
lyophilization, or the like method, whereby the surface treatment is
completed.
In this case, it is desirable that any of the above-mentioned treatment
steps mentioned above involve a heating step. The heating may be effected
during stirring the slurry composed of inorganic filler (A),
organo-phosphorus compound (1), and solvent; during evaporation of the
solvent; or after the evaporation. In particular, heating the slurry will
increase the dispersibility of the filler and thus allow it to be
surface-treated evenly. The heating temperature is preferably within the
range of 50.degree. C. to 150.degree. C. At temperatures below 50.degree.
C., the effect of heating will be poor, while heating at temperatures
exceeding 150.degree. C. may cause the double bond capable of radical
polymerization to react.
Those organophosphorus compounds (1) in which X.sub.2 is a hydroxyl or
mercapto group may also be used in the form of an alkali metal or ammonium
salt thereof so that they can be reacted with the inorganic filler in a
desalting reaction.
The dry method involves charging the inorganic filler (A) into a mixer,
such as a Henschel fluidizing mixer or a ribbon blender, and adding, while
stirring, the organophosphorus compound (1) directly or in the form of a
solution by spraying. In this case, the stirring is desirably carried out
with heating. This method is suited for the treatment of large-quantities
of the filler.
The organophosphorus compound is used preferably in an amount sufficient to
coat most of the inorganic filler surface with a monomolecular layer
thereof. The required amount can be estimated on the basis of the specific
surface area of inorganic filler, as measured by the BET method, and the
proportion of metal element on the surface of the filler. The required
quantity of organophosphorus compound increases with decreasing inorganic
filler diameter and increasing metal element content on the surface.
Generally speaking, in consideration of above factors, the
organosphosphorus compound (1) is used in an amount of 0.01 to 100 parts
by weight per 100 parts by weight of inorganic filler. Of course, the
optimal quantity of organophosphorus compound (1) should be determined
based on the results of preliminary experiments so that the physical
characteristics of the resinous composition for a specific use can be
maximized.
The quantity of organophosphorus compound (1) on inorganic filler (A) can
be estimated by elemental analysis, infrared spectroscopy, or fluorescent
X-ray analysis of the surface-treated inorganic filler.
Although a technique which comprises admixing a suitable amount of an
organophosphorus compound with a monomer and then admixing the untreated
inorganic filler with the resultant mixture to give a resinous composition
may be thought to be useful, this technique is undesirable, because it is
inferior in filler dispersibility, maximum filler content in the
composition, and mechanical strength of the resin product.
In addition, silica-based glass powders containing a metal element such as
barium or lanthanum, which are often used in composite resins for dental
use, have a large number of silanol groups on their surface. The
organophosphorus compound (1) is only poorly effective in the surface
treatment of the silanol groups, and hence, it gives unsatisfactory
results with the silica-based glass powders. Accordingly, in the case of
glass fillers having a high silica content, the combined use of the
organophosphorus compound (1) and a known silane coupling agent, such as
.gamma.-methacryloyloxypropyltrimethoxysilane, is preferable.
In this case, a two-step treatment process is employed which involves first
performing the surface treatment with the present organophosphorus
compounds and then carrying out a further surface treatment using a silane
coupling agent.
In a modified process, it is also possible to first carry out the treatment
with a silane coupling agent and then the treatment with the present
organophosphorus compound, or to perform both treatments in one step using
a mixture of the organophosphorus compound (1) and a silane coupling
agent.
The monomer capable of radical polymerization to be used in the composition
of the present invention should be copolymerizable with the
organophosphorus compound (1) used as the surface treating agent, and a
(meth)acrylate monomer is used as such monomer. The term "(meth)acrylate"
includes, within its meaning a methacrylate and an acrylate.
The composition according to the invention may contain, in addition to said
(meth)acrylate monomer, a small proportion of an ester of
.alpha.-cyanoacrylic, crotonic, cinnamic, sorbic, maleic, itaconic, or the
like acid with a mono- or dihydric alcohol, a (meth)acrylamide, such as
N-isobutylacrylamide, a vinyl ester, such as vinyl acetate, a vinyl ether,
such as butyl vinyl ether, a mono-N-vinyl compound, such as
N-vinylpyrrolidone and styrene derivatives.
Examples of the (meth)acrylate monomer are monofunctional (meth)acrylates,
such as methyl (meth)acrylate, ethyl (meth)acrylate, lauryl
(meth)acrylate, benzyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate and
dimethylaminoethyl (meth)acrylate; bifunctional monomers, such as ethylene
glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, neopentyl
glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, 1,10-decanediol
di(meth)acrylate, bisphenol A di(meth)acrylate,
2,2-bis[(meth)acryloyloxypolyethoxyphenyl]propane,
2,2-bis[4-(3-methacryloyloxy-2-hydroxypropoxy)phenyl] propane (hereinafter
sometimes referred to as "Bis-GMA") and the adduct of one mole of
2,2,4-trimethylhexamethylene diisocyanate with 2 moles of 2-hydroxyethyl
(meth)acrylate; trifunctional monomers, such as trimethylolpropane
tri(meth)acrylate; and tetrafunctional monomers, such as pentaerythritol
tetra(meth)acrylate and the adduct of one mole of
2,2,4-trimethylhexamethylene diisocyanate with 2 moles of glycerol
di(meth)acrylate. These mono- and polyfunctional (meth)acrylates may be
used either singly or in the form of a mixture of two or more.
In addition to the above-mentioned monomers, known adhesive monomers may
desirably be used in combination, particularly in cases where an
adhesiveness to the tooth substance or to dental metals is expected. Such
monomers contain an acidic group in their structure. The acidic group here
includes, not only in its narrow sense, such groups as
##STR39##
but also in its broad sense, acid anhydride groups such as
##STR40##
and acid halide groups such as
##STR41##
(in which Z.sub.1 is F, Cl, Br, or I).
Specific examples of the adhesive monomers are:
##STR42##
The proportion of surface-treated inorganic filler to polymerizable monomer
may vary widely depending on the intended use of the resinous composition
but, generally, it is within the range of 0.01 to 100 parts by weight of
surface-treated inorganic filler per 1 part by weight of polymerizable
monomer. A more detailed discussion of the proportion is contained later
herein.
The composition of the present invention may further contain, if necessary,
one or more other fillers than the inorganic filler. The other fillers may
be either of an inorganic nature or of an organic nature and, as inorganic
fillers, there may be mentioned, for example, silica-based inorganic
fillers such as quartz, amorphous silica and borosilicate glass. These
fillers are used after preliminary surface treatment with a silane
coupling agent. As organic fillers, there may be mentioned poly(methyl
methacrylate), poly(vinyl chloride), polystyrene and other polymer powders
as well as such organic-inorganic composite fillers or prepolymerized
microfillers as disclosed in Japanese Laid-Open Patent Application Kokai
No. 56-49311.
The composition of the present invention, which essentially comprises an
inorganic filler and a polymerizable monomer, may be converted to a cured
product by subjecting it to heating at a temperature not lower than
100.degree. C. or to irradiation with light or electron beams. Another
method to cure the composition is adding an initiator to facilitate the
polymerization.
The initiator to be used in the practice of the present invention is not
limited to any particular species but may be any of the known initiators.
The initiator is generally selected in consideration of the
polymerizability of the monomer and the polymerization conditions. Thus,
for instance, when a (meth)acrylate is subjected to high-temperature
polymerization, an organic peroxide, such as benzoyl peroxide (hereinafter
referred to as "BPO"), di-tert-butyl peroxide or cumene hydroperoxide, or
an azo compound such as 2,2'-azobisisobutyronitrile or
1,1'-azobis(cyclohexane-1-carbonitrile) is used.
On the other hand, for room temperature polymerization, oxidation-reduction
(redox) initiators, such as benzoyl peroxide/dimethylaniline, cumene
hydroperoxide/thiourea, ascorbic acid/Cu.sup.2+ salt, and organic
sulfinic acid (or salt thereof)/amine/peroxide, and, further,
tributylborane, and organic sulfinic acids are suitably used.
In cases where photopolymerization is carried out by irradiation with
visible light, redox initiators, such as .alpha.-diketone/tertiary amine,
.alpha.-diketone/aldehyde, and .alpha.-diketone/mercaptan, are preferred.
The .alpha.-diketone is, for example, camphor quinone, diacetyl,
2,3-pentanedione, benzil, acenaphthene quinone or phenanthraquinone. The
tertiary amine is, for example, N,N-dimethylaminoethyl methacrylate, ethyl
N,N-dimethylaminobenzoate or Michler's ketone. The aldehyde is, for
example, citronellal, lauryl aldehyde, o-phthaldialdehyde or
p-octyloxybenzaldehyde, and the mercaptan is, for example, 1-decanethiol,
thiosalicylic acid, 2-mercaptobenzoxazole or 4-mercaptoacetophenone.
Furthermore, an .alpha.-diketone/organic peroxide/reducing agent initiator
system derived from the above-mentioned redox initiator with addition of
an organic peroxide is also suitable. For photopolymerization under
ultraviolet irradiation, 2,4,6-trimethylbenzoyldiphenylphosphine oxide,
benzoin methyl ether, benzil dimethyl ketal, benzophenone,
2-methylthioxanthone, diacetyl, benzil, azobisisobutyronitrile and
tetramethylthiuram disulfide are suitably used as well as the
above-mentioned initiators for photopolymerization under visible light.
These polymerization initiators are used suitably in an amount within the
range of 0.01 to 10% by weight based on the polymerizable monomer.
The resinous composition of the present invention may further contain a
polymerization inhibitor, ultraviolet absorber, fluorescent pigment, and
pigment if necessary.
The essential components of the resinous composition according to the
invention, namely the inorganic filler and polymerizable monomer, can be
selected respectively from the above-mentioned substances or compounds so
that a wide range of application of said composition can be covered.
In the field of dentistry, the composition according to the invention is
required to meet high strength and aesthetic (in particular transparency)
requirements so that it can be used as a composite resin for dental
application. To meet these requirements, it is recommended that an alumina
filler having a refractive index of 1.60 to 1.70, a (meth)acrylate monomer
which can give a refractive index of 1.50 to 1.60 after curing by
polymerization, and a silica-based inorganic filler having a refractive
index of 1.50 to 1.60 be used in combination. The use of such components,
which are close in refractive index to one another, can result in good
transparency as well as improved mechanical properties owing to the
addition of the alumina filler. In this case, the particle size and amount
of the fillers can be suitably selected depending on the intended use of
the composition.
For use as a dental adhesive intended for adhesion to the tooth, in
particular to the dentin, the composition should desirably contain an
inorganic filler having good biocompatibility. As such a filler, there may
be mentioned, for example, hydroxyapatite, calcium phosphate, calcium
hydrogen phosphate, calcium diphosphate, calcium metaphosphate, calcium
pyrophosphate, and various kinds of bioglass. It is also possible to use a
fluorine-containing inorganic filler, such as calcium fluoride, for the
purpose of reinforcing the tooth substance. These fillers are
surface-treated with the organophosphorus compound (1).
As the polymerizable monomer component, a system comprising the
above-mentioned (meth)acrylate monomer and adhesive monomer is used. The
fillers are incorporated in the composition in an amount of 0.5 to 20
parts by weight per one part by weight of the polymerizable monomer
component.
When the dental adhesive should serve as a fissure sealant, metal oxides,
such as alumina, titanium oxide, and zirconium oxide, and calcium fluoride
are preferred inorganic fillers, and these fillers are used in an amount
of 0.01 to 5 parts by weight per one part by weight of the polymerizable
monomer component.
The resinous composition according to the invention may be formulated in
various forms depending on the intended use. Examples are as follows:
(i) One-package paste or liquid form
The filler, polymerizable monomer, and polymerization initiator are
combined into a paste or liquid. The initiator is a photopolymerization
initiator and/or an initiator for medium or high temperature
polymerization.
(ii) Two-package paste or liquid form
The oxidizing agent and reducing agent of an oxidation-reduction type
polymerization initiator system capable of catalyzing room temperature
polymerization are each separately admixed with either the filler or
polymerizable monomer to give two paste or liquid packages.
(iii) Powder-liquid form
This form is composed of a powder which is a mixture of the above-mentioned
reducing agent (or oxidizing agent) and a filler powder and a solution
(liquid) of the above-mentioned oxidizing agent (or reducing agent) in the
polymerizable monomer or monomers.
(iv) Cured article form
The composition in the above-mentioned form (i), to (iii) is molded and
cured by polymerization. An artificial tooth is an example of this form.
When offered in the semi-finished forms, (i) to (iii), to dentists or
dental technicians, the composition is molded and cured by polymerization
by the user and thus, functions as a dental material.
The composite material comprising a metal element-containing,
water-insoluble inorganic filler surface-treated in advance with the
organophosphorus compound (1) and a monomer capable of radical
polymerization is a high performance composition, which has never been
attained in the prior art, namely with composite materials in which the
above-mentioned inorganic filler or a silica-based filler is treated with
a known silane coupling agent. For example, surface modification with
silane coupling agents is almost ineffective for metal salt powders, such
as calcium carbonate, calcium phosphate and hydroxyapatite and, therefore,
composite materials containing these fillers possess poor mechanical
strength and cannot be used for dental materials. In contrast, when the
organophosphorus compound (1) is used in the surface treatment of metal
salts, adhesion between the filler and matrix resin is markedly increased,
so that high-strength dental materials can be obtained with metal salts as
fillers.
For metal powders as well, the effect of surface modification with silane
coupling agents is poor, and, moreover, composite materials containing
silane treated metal powders rapidly lose their strength under wet
conditions and, therefore, can hardly be employed as dental materials. In
contrast, when the organophosphorus compound (1) is used for surface
treatment, composite dental materials showing much improved initial
strength and wet strength can be obtained.
Surface treatment with the organophosphorus compound (1) is also markedly
effective for metal oxide fillers, such as aluminum oxide or titanium
oxide fillers, for which surface treatment with silane coupling agents is
effective to a considerable extent but does not always give satisfactory
water resistance to the resin matrix-filler adhesion. The use of said
organophosphorus compound (1) thus makes it possible to incorporate said
fillers in composite resins for dental use.
Another outstanding feature of the present invention is that high loading
of resin matrices with inorganic fillers is possible. The so-called
submicron fillers, which have a particle size of not more than 1 .mu.m,
produce a marked viscosity increase and therefore can hardly be
incorporated in polymerizable monomers at high concentrations, even after
surface treatment with known silane coupling agents.
The difficulty is great, particularly when filler particles are ultrafine,
that is having a particle size of not more than 0.1 .mu.m. In contrast,
submicron fillers which have been surface-treated with the
organophosphorus compound (1), show a low increase of viscosity and can be
incorporated into resin matrices in amounts 1.5 to 3 times as large as the
inorganic filler treated with a known silane coupling agent. Thus, it is
now possible to further improve the hardness, compressive strength, wear
resistance, and other aspects of composite resins for dental use.
A further feature of the present invention consists of improved aesthetic
features and radiopacity of composite resins for dental use. Since metal,
in particular heavy metal, element-containing fillers have great
radiopacity, composite resins having a larger radiopacity than enamel can
be readily prepared by using these fillers in large amounts.
Furthermore, resinous compositions having a refractive index close to that
of natural teeth (n=1.61.about.1.63) can be obtained by using an inorganic
filler which contains a metal element and has a larger refractive index
than quartz (n=1.55), and thus, the resinous composition shows improved
aesthetic features, e.g., reflection and refraction indexes, comparable to
those of natural teeth.
The present invention is applicable to materials for biological hard
tissues. More specifically, the invention can be applied to composite
resins for dental use (e.g., restorative filling materials; prosthetic
materials for inlays, crowns, and the like; materials for artificial
teeth; and abutment construction materials) as well as to dental adhesives
(e.g., bonding agents, resin cements, and fissure sealants), materials for
denture bases, and impression materials, contributing to the improvement
of these dental materials.
In the field of orthopedics, the present invention can provide
hydroxyapatite-containing bone cement, artificial bone resulting from
compounding hydroxyapatite and an organic polymer, and ceramic
whisker-reinforced artificial bone.
For industrial purposes, the composition according to the present invention
can be used as a material for the manufacture of artificial marble,
decorative panels and various machine parts.
Other features of the invention will become apparent in the course of the
following descriptions of exemplary embodiments which are given for
illustration of the invention and are not intended to be limiting thereof.
EXAMPLES
EXAMPLE 1
A flask was charged with 50 g of alumina (Showa Denko, AL-160 SG-4.RTM.)
having an average particle size of 0.9 .mu.m and a specific surface area
of 5.4 m.sup.2 /g as measured by the Brunauer, Emmett, and Teller (BET)
method, 200 ml of toluene and 3 g of 10-methacryloyloxydecyl dihydrogen
phosphate, and the mixture was refluxed for 2 hours with vigorous stirring
and then allowed to cool. The alumina powder was recovered from the
suspension by filtration, washed thoroughly with toluene, dried under
vacuum for 12 hours and then heated in air at 90.degree. C. for 2 hours,
to give a surface-treated filler. The adsorption of
10-methacryloyloxydecyl dihydrogen phosphate was estimated to be 1.2 parts
by weight per 100 parts by weight of the alumina powder based on the
phosphorus content determined by fluorescent X-ray analysis, of the
powder.
Then, a polymerizable monomer composition was, prepared by mixing together
35 parts by weight ob 2,2-bis[methacryloyloxypolyethoxyphenyl]propane (a
molecule containing, on an average, 2.6 ethoxy groups; hereinafter
referred to as "D-2.6E"), 40 parts by weight of the adduct of one mole of
2,2,4-trimethylhexamethylene diisocyanate and 2 moles of glycerol
dimethacrylate (hereinafter referred to as "U-4TH"), 25 parts by weight of
neopentyl glycol dimethacrylate (hereinafter referred to as "NPG") and 1
part by weight of benzoyl peroxide. Thirty parts by weight of this
composition and 70 parts by weight of the above surface-treated filler
were kneaded together to give a pasty polymerizable composition.
This composition was evaluated for the following characteristics:
(i) Consistency
A filler more wettable with a polymerizable monomer will have a better
dispersibility in the polymerizable monomer and give a resultant
composition lower in viscosity. Therefore, the effect of the surface
treatment can be judged by measuring the consistency of the composite as
an index of the viscosity. In this experiment, the value measured in the
following manner was defined as "consistency". 0.5 ml of the paste was
heaped in the middle of a glass plate (5.times.5 cm). Another glass plate
(5.times.5 cm) was then gently placed thereon under a load of 40 g. After
120 seconds, the major and minor axes of the spread paste body were
measured through the upper glass plate. The arithmetic mean of both the
values was taken as the consistency. The consistency values shown in Table
1 are the mean of three independent measurements.
(ii) Flexural strength
The flexural strength was measured as an index of the adhesion strength of
the filler to the resin matrix in the polymerized composition. The above
paste was filled into a 2.times.2.times.30 mm mold and cured by heating at
130.degree. C. for 1 hour, and the cured article was then taken out of the
mold. The thus-obtained square rod specimen was stored in air at
37.degree. C. for 1 day and then subjected to a three-contact-point
flexural test (span between terminal bearing edges=20 mm; cross head
speed=1 mm/minute) on an Instron universal tester. The results shown in
Table 1 are the mean of 10 measurements (10 test specimens).
(iii) Water resistance in terms of flexural strength
Test specimens, prepared by the method described in the flexural strength
test (ii), were subjected to accelerated degradation by immersion in water
at 70.degree. C. for 10 days and then tested for flexural strength. The
water resistance can be evaluated by comparing the flexural strength after
water immersion with the initial flexural strength. The mean value from 10
test specimens is shown in Table 1.
EXAMPLES 2-41
The procedure of Example 1 was followed using the organophosphorus
compounds shown in Table 1 in lieu of 10-methacryloyloxydecyl dihydrogen
phosphate used in Example 1, and the pastes obtained were evaluated in the
same manner as in Example 1. The results are shown in Table 1.
TABLE 1
__________________________________________________________________________
Flexural strength
(kg/cm.sup.2)
Paste After 10
consis- days in
tency water at
No. Surface-treating agent (mm) Initial
70.degree.
__________________________________________________________________________
C.
Example 1
##STR43## 35 1049
932
Example 2
##STR44## 23 758
606
Example 3
##STR45## 33 1015
908
Example 4
##STR46## 40 1064
961
Example 5
##STR47## 26 783
655
Example 6
##STR48## 35 971
816
Example 7
##STR49## 29 926
832
Example 8
##STR50## 34 1028
915
Example 9
##STR51## 31 879
790
Example 10
##STR52## 29 892
796
Example 11
##STR53## 30 792 641
Example 12
##STR54## 29 973 892
Example 13
##STR55## 31 1010
881
Example 14
##STR56## 32 1013
896
Example 15
##STR57## 38 1065
911
Example 16
##STR58## 32 892
794
Example 17
##STR59## 31 872
763
Example 18
##STR60## 35 1001
900
Example 19
##STR61## 24 712
570
Example 20
##STR62## 37 967
855
Example 21
##STR63## 43 992
861
Example 22
##STR64## 26 742
609
Example 23
##STR65## 25 725
600
Example 24
##STR66## 36 901
773
Example 25
##STR67## 36 942
870
Example 26
##STR68## 24 700
602
Example 27
##STR69## 28 842
764
Example 28
##STR70## 33 1006
915
Example 29
##STR71## 39 1012
940
Example 30
##STR72## 33 996
935
Example 31
##STR73## 32 982
924
Example 32
##STR74## 34 912
831
Example 33
##STR75## 31 876
812
Example 34
##STR76## 33 904
810
Example 35
##STR77## 26 705
629
Example 36
##STR78## 34 883
755
Example 37
##STR79## 34 971
896
Example 38
##STR80## 26 731
623
Example 39
##STR81## 35 915
822
Example 40
##STR82## 34 950
866
Example 41
##STR83## 33 967
892
__________________________________________________________________________
COMPARATIVE EXAMPLE 1
A paste was prepared by using the same alumina powder as used in Example 1
but without any surface treatment, and the consistency and flexural
strength measurements were made in the same manner as in Example 1. The
results are shown in Table 2.
COMPARATIVE EXAMPLES 2-5
The same evaluations as made in Example 1 were performed using the alumina
powder surface-treated with one of the organophosphorus compounds shown in
Table 2 in lieu of the organophosphorus compound used in Example 1. The
results thus obtained are shown also in Table 2.
COMPARATIVE EXAMPLE 6
A paste was prepared by adding 69.17 parts by weight of the same alumina
powder as used in Example 1, without surface treatment, to a mixture of 30
parts by weight of the same polymerizable monomer composition as used in
Example 1 and 0.83 part by weight of 10-methacryloyloxydecyl dihydrogen
phosphate, followed by kneading, and consistency and flexural strength
measurements were performed in the same manner as in Example 1. The
results obtained are shown in Table 2. As compared with the product
obtained in Example 1, the product in this comparative example showed a
marked decrease in flexural strength.
TABLE 2
__________________________________________________________________________
Flexural strength
Paste (kg/cm.sup.2)
consistency
After 10 day in
No. Surface-treating agent
(mm) Initial
in water at 70.degree. C.
__________________________________________________________________________
Comparative
Example
1 None 11 530 390
##STR84## 15 560 500
3
##STR85## 20 610 510
4
##STR86## 16 550 490
5
##STR87## 16 600 480
6 None 27 814 583
__________________________________________________________________________
EXAMPLES 42-50
A mixture of 40 g of powdery titanium oxide (of the rutile structure;
average particle size=0.2 .mu.m), 400 ml of toluene and 4 g of one of the
organophosphorus compounds shown in Table 3 was heated under reflux for 2
hours and then allowed to cool. The titanium oxide powder was filtered
off, washed with toluene, dried under vacuum and subjected to a dry heat
treatment at 90.degree. C. for 2 hours to give a surface-treated filler.
A paste was prepared by mixing and kneading together 50 parts by weight of
the same polymerizable monomer composition as used in Example 1 and 50
parts by weight of the above filler. This paste was subjected to
consistency and flexural strength measurements in the same manner as in
Example 1. The results obtained are shown in Table 3.
COMPARATIVE EXAMPLES 7-11
Pastes were prepared as in Example 42 using a surface-treated filler
prepared by treatment of the above-mentioned titanium oxide powder with
one of the organophosphorus compounds shown in Table 3 or using said
titanium oxide powder without any surface treatment. Consistency and
flexural strength measurements were made in the same manner as in Example
1. The results obtained are shown in Table 3.
TABLE 3
__________________________________________________________________________
Flexural strength
Paste (kg/cm.sup.2)
consistency
After 10 days
No. Surface-treating agent (mm) Initial
in water at 70.degree.
__________________________________________________________________________
C.
Example
42
##STR88## 24 648 556
43
##STR89## 41 839 773
44
##STR90## 45 860 810
45
##STR91## 45 875 834
46
##STR92## 32 672 594
47
##STR93## 25 644 581
48
##STR94## 38 825 762
49
##STR95## 40 793 699
50
##STR96## 39 832 765
Comparative
Example
##STR97## 18 512 435
8
##STR98## 19 591 458
9
##STR99## 19 588 452
10
##STR100## 20 524 447
11 None 15 503 391
__________________________________________________________________________
EXAMPLES 51-59
50 g of a hydroxyapatite powder (average particle size=75 .mu.m) was
admixed with 150 ml of toluene and 1 g of one of the organophosphorus
compounds shown in Table 4 and surface-treated by following the procedure
of Example 1. A paste was prepared by mixing and kneading together 80
parts by weight of this filler and 20 parts by weight of the same
polymerizable monomer composition as used in Example 1. The paste was
subjected to the same consistency and flexural strength measurements as
performed in Example 1. The results obtained are shown in Table 4.
COMPARATIVE EXAMPLES 12-16
Pastes were prepared as in Example 51 using a filler prepared by surface
treatment of the above-mentioned hydroxyapatite powder with one of the
organophosphorus compounds shown in Table 4 or using said powder without
any surface treatment. The pastes were subjected to the same consistency
and flexural strength measurements as performed in Example 1. The results
are shown in Table 4.
TABLE 4
__________________________________________________________________________
Flexural strength
Paste (kg/cm.sup.2)
consistency
After 10 days
No. Surface-treating agent (mm) Initial
in water at 70.degree.
__________________________________________________________________________
C.
Example
51
##STR101## 25 471 352
52
##STR102## 36 539 442
53
##STR103## 38 560 450
54
##STR104## 40 606 557
55
##STR105## 41 533 414
56
##STR106## 29 497 380
57
##STR107## 35 556 439
58
##STR108## 36 515 412
59
##STR109## 37 550 422
Comparative
Example
12
##STR110## 17 392 283
13
##STR111## 20 400 260
14
##STR112## 19 420 285
15
##STR113## 21 405 274
16 None 12 359 218
__________________________________________________________________________
EXAMPLE 60-63
A flask was charged with 50 g of a silver powder (particle size .ltoreq.50
.mu.m), 100 ml of toluene and 0.5 g of one of the organophosphorus
compounds shown in Table 5 and then the procedure of Example 1 was
followed to give a surface-treated filler. A paste was prepared by mixing
and kneading together 93 parts by weight of the filler and 7 parts by
weight of the same polymerizable monomer composition as used in Example 1.
The paste was subjected to the same consistency and flexural strength
measurements as performed in Example 1. The results are shown in Table 5.
COMPARATIVE EXAMPLES 17 and 18
Pastes were prepared as in Example 60 using a filler prepared by surface
treatment of the above-mentioned silver powder with one of the
organophosphorus compounds shown in Table 5 or using said powder without
any surface treatment. The pastes were subjected to the same consistency
and flexural strength measurements as performed in Example 1. The results
are shown in Table 5.
TABLE 5
__________________________________________________________________________
Flexural strength
Paste (kg/cm.sup.2)
consistency
After 10 days in
No. Surface-treating agent
(mm) Initial
water at 70.degree. C.
__________________________________________________________________________
Example
60
##STR114## 35 924 784
61
##STR115## 43 1015
978
62
##STR116## 43 991 964
63
##STR117## 46 1125
1046
Comparative
Example
17
##STR118## 21 621 286
18 None 15 305 171
__________________________________________________________________________
EXAMPLE 64
A La glass ceramic (Schott,, GM-31684.RTM.; n=1.56) was ground in a
vibrating ball mill to give a powder having a particle size range of 0.1
to 20 .mu.m and an average particle size of 2.8 .mu.m. This powder was
surface-treated in the conventional manner with
.gamma.-methacryloyloxypropyltrimethoxysilane, which was used in an amount
of 2 parts by weight per 100 parts by weight of said powder, to give a
surface treated filler. Separately, a mixture of 50 g of microfine alumina
(Nippon Aerosil, aluminum oxide C.RTM.) having an average particle size of
0.02 .mu.m, a specific surface area of 100 m.sup.2 /g, as measured by the
BET method, and a refractive index of n=1.65, 15 g of
10-methacryloyloxydecyl dihydrogen phosphate and 500 ml of toluene was
heated under reflux for 3 hours and then allowed to cool. The filler was
recovered by centrifugation, dried under vacuum for 24 hours and then
further heated in air at 90.degree. C. for 2 hours to give a
surface-treated microfine alumina powder filler. Elemental analysis of
this alumina powder revealed an ash content of 85.5% by weight. The same
polymerizable monomer composition (n=1.528) as used in Example 1 was used
as the polymerizable monomer component except that 0.5 part by weight of
2,4,6-trimethylbenzoyldiphenylphosphine oxide was added per 100 parts by
weight of said composition in lieu of BPO.
A polymerizable composition (paste) was prepared by mixing and kneading
together 500 parts by weight of the above surface-treated La glass filler,
180 parts by weight of the surface-treated microfine alumina filler and
100 parts by weight of the polymerizable monomer composition, followed by
deaeration under vacuum. This paste was polymerized by curing by a
90-second exposure to photoirradiation using a xenon lamp (Kulzer,
Dentacolor XS.RTM.), followed by heating for 30 minutes, at 120.degree. C.
The thus-obtained cured product was measured for flexural strength,
compressive strength, Brinell hardness and transparency. The results
obtained are shown in Table 6.
The definitions of the measured quantities and the methods of measurement
as used in this example are as follows:
(i) Flexural strength
The same mold as used in Example 1 was employed and polymerization was
carried out in the same manner as described above. The thus-obtained
moldings were immersed in water at 37.degree. C. for 24 hours and then
subjected to three-contact-point flexural testing using an Instron
universal tester (cross head speed: 1 mm/minute; span between bearing
edges: 20 mm). The value is the mean from 10 test specimens.
(ii) Compressive strength
The paste was filled into a cylindrical mold, 4 mm in diameter and 4 mm in
height, and polymerized as described above. The molded article was taken
out of the mold, immersed in water at 37.degree. C. for 24 hours and then
tested on an Instron universal tester at a cross head speed of 2
mm/minute. The value reported is the mean from 10 test specimens.
(iii) Brinell hardness
The paste was filled into a mold having a diameter of 10 mm and a thickness
of 5 mm, a cover glass was brought into contact with the upper surface of
the paste under pressure, and polymerization was carried out as described
above.
The cured product was taken out of the mold, and the face that had been
kept in contact with the glass was polished with an abrasive paper with
220 grit to a depth of 0.5 mm and subjected to testing.
(iv) Transparency
The paste was molded into a disk (20 mm .phi..times.0.85 mm) and, after
curing as described above, the molding was used as a test specimen. For
the transparency evaluation, a colorimeter (Nippon Denshoku model
.SIGMA.80) was used, the lightness (L.sub.1) was measured with a standard
white plate located behind the test specimen on one hand and, on the
other, the lightness (L.sub.2) was measured with a standard black plate
placed behind the same test specimen. The difference, .DELTA.L=L.sub.1
-L.sub.2, was used as an index of transparency. A greater .DELTA.L value
means a higher level of transparency.
(v) Refractive index
The refractive indices of the alumina and inorganic fillers were measured
with an Abbe refractometer by the immersion method in a solvent of
sulfur-containing diiodomethane, bromonaphthalene, methyl salicylate, or
dimethylformamide and using the D line of a sodium lamp as a light source.
The refractive index of the polymerizable monomer composition after curing
was measured with an Abbe refractometer using, as the test specimen, a
cured rectangular parallelepiped molding (5 mm.times.10 mm.times.20 mm)
prepared by deaerating the polymerizable monomer composition containing
0.5% by weight of benzoyl peroxide and then polymerizing the same at
110.degree. C. for 30 minutes.
(vi) Average particle size and particle size range
For the microfine alumina powder, the particle size was determined based on
a transmission electron photomicrograph.
For the La glass ceramic, a Horiba model CAPA 500 particle size
autoanalyzer was used. The measurement was made with the centrifugal and
gravitational sedimentation-light transmission technique.
EXAMPLE 65
A cured product obtained by photopolymerization of the same paste used in
Example 64, but without heating, was tested in the same manner as in the
same Example. The results are also shown in Table 6.
COMPARATIVE EXAMPLE 19
An alumina filler was prepared by surface-treating 100 parts by weight of
the same microfine alumina powder as used in Example 64 with 30 parts by
weight of .gamma.-methacryloyloxypropyltrimethoxysilane in the
conventional manner. An attempt was made to prepare a composition using
this alumina filler and the same La glass ceramic and polymerizable
monomer composition as used in Example 64 with the same compounding ratio.
However, the viscosity was so high that kneading was impossible.
COMPARATIVE EXAMPLE 20
A microfine silica filler was prepared by surface-treating 100 parts by
weight of a microfine silica powder (Nippon Aerosil, Aerosil 130.RTM.:
average particle size 0.016 .mu.m; BET specific surface area 130 m.sup.2
/g) with 30 parts by weight of
.gamma.-methacryloyloxypropyltrimethoxysilane in the conventional manner.
An attempt was made to prepare a composition using the microfine silica
filler in lieu of the microfine alumina filler used in Example 64,
together with the same La glass ceramic and polymerizable monomer
composition in the same compounding ratio as used in Example 64. However,
the viscosity was so high that kneading was impossible.
COMPARATIVE EXAMPLE 21
A microfine silica filler was prepared by surface-treating 100 parts by
weight of a microfine silica powder (Nippon Aerosil, Aerosil OX-50.RTM.;
average particle size 0.04 .mu.m; BET specific surface area 50 m.sup.2 /g)
with 15 parts by weight of .gamma.-methacryloyloxypropyltrimethoxysilane
in the conventional manner. Said silica filler was mixed and kneaded with
the same La glass ceramic and polymerizable monomer composition as used in
Example 64 in the same compounding ratio as used therein, the silica
filler being used in lieu of the microfine alumina filler. The resultant
composition was cured by the same polymerization method used in Example
64, and test specimens thus-obtained were subjected to the same tests
described above. The results are shown in Table 6.
EXAMPLE 66
A polymerizable monomer composition was prepared by mixing together 40
parts by weight of D-2.6E, 40 parts by weight of 1,10-decanediol
dimethacrylate, 20 parts by weight of U-4TH and 1 part by weight of
benzoyl peroxide (BPO). A polymerizable composition in the form of a paste
was prepared by mixing and kneading together 100 parts by weight of this
polymerizable monomer composition and 250 parts by weight of the same
microfine alumina filler used in Example 64. This paste was cured by
heating at 130.degree. C. for 1 hour to effect polymerization, and the
cured product was tested in the same manner as in Example 64. The test
results are also shown in Table 6.
COMPARATIVE EXAMPLE 22
250 parts by weight of the same surface-treated alumina filler used in
Example 19 were mixed with 100 parts by weight of the same polymerizable
monomer composition used in Example 66. However, the mixture did not give
a paste suited for use as a dental material; kneading was impossible.
COMPARATIVE EXAMPLE 23
The procedure of Example 66 was followed except for using 200 parts by
weight of the same microfine silica filler used in Comparative Example 21
and 100 parts by weight of the same polymerizable monomer composition used
in Example 66. The evaluation results are shown in Table 6.
EXAMPLE 67
The cured product produced in Example 66 was ground in a vibrating ball
mill and then sifted to give a powder having a particle size range of 0.1
.mu.m to 100 .mu.m and an average particle size of 15 .mu.m. Separately, a
polymerizable monomer composition was prepared by mixing together 70 parts
by weight of D-2.6E, 30 parts by weight of 1,6-hexanediol dimethacrylate
and 0.5 part by weight of 2,4,6-trimethylbenzoyldiphenylphosphine oxide. A
polymerizable composition was prepared by mixing and kneading together 20
parts by weight of said monomer composition, 55 parts by weight of the
above-described powder and 25 parts by weight of the same microfine
alumina filler used in Example 64. The cured product obtained from this
composition by the same polymerization method used in Example 64 was
tested in the same manner. The results are shown in Table 6.
COMPARATIVE EXAMPLE 24
The cured product produced in Comparative Example 23 was ground in a
vibrating ball mill and then sifted to give a powder having a particle
size range of 0.1 .mu.m to 100 .mu.m and an average particle size of 14
.mu.m.
A polymerizable composition was prepared by mixing and kneading together 20
parts by weight of the same polymerizable monomer composition used in
Example 67, 55 parts by weight of the this powder, and 25 parts by weight
of the same microfine silica filler used in Comparative Example 21. The
same evaluation tests performed in Example 67 were carried out, and the
results are shown in Table 6.
TABLE 6
__________________________________________________________________________
Comparative Comparative Comparative
Example 64
Example 21
Example 65
Example 66
Example 23
Example
Example
__________________________________________________________________________
24
Flexural strength
1650 1250 1510 880 650 1020 860
(kg/cm.sup.2)
Compressive strength
5910 3920 4690 4350 3760 4600 3970
(kg/cm.sup.2)
Brinell hardness
88 70 71 48 40 45 38
Transparency .DELTA.L
38 8 38 45 43 43 22
__________________________________________________________________________
EXAMPLE 68
The same hydroxyapatite powder used in Example 51 was ground in a rotary
ball mill to give a powder having an average particle size of 4.5 .mu.m.
50 g of this powder was mixed with 150 ml of toluene and 1.5 g of
10-methacryloyloxydecyl dihydrogen phosphate, and surface treatment was
carried out by following the procedure of Example 1. A two-package
adhesive (liquid and powder) was prepared using the thus-obtained filler
and according to the following formulation;
______________________________________
Composition A (liquid)
D-2.6E 50 parts by weight
NPG 25 parts by weight
2-Hydroxyethyl methacrylate
10 parts by weight
10-methacryloyloxydecyl
15 parts by weight
dihydrogen phosphate
Benzoyl peroxide 1 part by weight
Hydroquinone monomethyl
0.05 part by weight
ether
Composition B (powder)
Surface-treated hydroxy-
100 parts by weight
apatite filler mentioned
above
Sodium benzenesulfinate
0.3 part by weight
N,N-Diethanol-p-toluidine
0.3 part by weight
______________________________________
In preparing composition B, the filler was sprayed with a solution of the
sodium benzenesulfinate and N,N-diethanol-p-toluidine in 10 parts by
weight of methanol, and then the methanol was evaporated.
A test for adhesion to human dentin was conducted using compositions A and
B. The dentin of a human molar was exposed by cutting the crown portion
off with a cutter while pouring water thereonto. The dentin surface was
etched with 40% aqueous orthophosphoric acid for 1 minute, washed with
water and then dried with an air syringe. A double adhesive tape piece
having a 5 mm .phi. perforation was then applied to said surface. The
tooth was fixed horizontally, and a plastic ring (6 mm in inside diameter,
5 mm in height) was placed concentrically on the perforation of the tape.
Appropriate quantities of compositions A and B were kneaded together in
the weight ratio of 1:4 for about 1 minute and, when the mixture became a
soft paste, the paste was put into the plastic ring, then a hook for
tensile testing was set in the paste, and the specimen was allowed to
stand for 30 minutes and then immersed in water at 37.degree. C. for 24
hours. Thereafter, the adhesive strength was measured using an Instron
universal tester at a cross head speed of 2 mm/minute. The value is a mean
of 5 test specimens. The initial flexural strength of this cured product
and the flexural strength after 10 days of immersion in water at
70.degree. C. were also measured. The results of these measurements are
shown in Table 7.
COMPARATIVE EXAMPLE 25
An adhesive was prepared according to the same formulation as given in
Example 68 except that .gamma.-methacryloyloxypropyltrimethoxysilane was
used as the surface-treating agent in lieu of the 10-methacryloyloxydecyl
dihydrogen phosphate used in Example 68, and the surface treatment was
performed in the conventional manner. The adhesive was tested in the same
manner as in Example 68. The results are also shown in Table 7.
COMPARATIVE EXAMPLE 26
An adhesive was prepared according to the same formulation as used in
Example 68 except that the same hydroxyapatite powder used in Example 51
was used without surface treatment in lieu of the surface-treated
hydroxyapatite filler. The adhesive was tested in the same manner, and the
results are also shown in Table 7.
TABLE 7
______________________________________
Adhesive Flexural strength (kg/cm.sup.2)
strength After 10 days
(kg/cm.sup.2)
Initial in water at 70.degree. C.
______________________________________
Example 68 117 928 806
Comparative
98 853 615
Example 25
Comparative
91 864 596
Example 26
______________________________________
EXAMPLE 69
The same hydroxyapatite powder used in Example 51 was ground in a vibrating
ball mill to give a powder having an average particle size of 2.3 .mu.m.
200g of this powder was mixed with 600 ml of toluene and 10 g of
10-methacryloyloxydecyl dihydrogen phosphate, and surface treatment was
carried out as in Example 69. A polymerizable composition was prepared by
mixing together 75 parts by weight of the surface-treated filler, 20 parts
by weight of methyl methacrylate, 5 parts by weight of 1,10-decanediol
dimethacrylate and 0.1 part by weight of benzoyl peroxide. The composition
was put into a mold and heated under pressure at 140.degree. C. for 1 hour
to effect polymerization. Thus was obtained a molding having
biocompatibility and physical properties suitable for use as an artificial
tooth root or an artificial bone.
EXAMPLE 70
Three pastes were prepared by adding a coloring agent to the
photopolymerizable composition prepared in Example 64 so that they could
have the respective chromaticities of the cured products given in Table 8.
The color tones match those of tooth neck, dentin, and enamel,
respectively. A gold-silver-palladium alloy (GC Corp., Castwell.RTM.) was
cast into a metal frame suited for use as a crown for a resin facing for
the maxillary central incisor. The frame was coated with an opaquer
(Kulzer Dentacolor.RTM. opaquer A-20) for masking the metallic color
thereof and subjected to photoirradiation for 90 seconds using a xenon
lamp (Kulzer Dentacolor XS.RTM.). The paste prepared for tooth neck was
applied thereto and photoirradiated for 30 seconds, then the paste for
dentin was placed thereon and photoirradiated for 30 seconds, and the
paste for enamel was further layered thereon and photoirradiated for 90
seconds. The complete article was placed in a hot air drier and heated at
120.degree. C. for 20 minutes, and then allowed to cool. After trimming
and buffing, there was obtained a nice facing crown.
TABLE 8
______________________________________
No. a* b* L*
______________________________________
1. (For tooth neck)
0.08 26.82 71.50
2. (For dentin)
-2.28 19.98 76.20
3. (For enamel)
-1.01 5.45 80.03
______________________________________
*A disk of cured product, 0.85 mm in thickness and about 20 mm in
diameter, was prepared and the chromaticity was measured with a
colorimeter (Nippon Denshoku model .SIGMA.80) with a standard white plate
in the background.
Obviously, numerous modifications and variations of the present invention
are possible in light of the above teachings. It is therefore to be
understood that within the scope of the appended claims, the invention may
be practiced otherwise than as specifically described herein.
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